1. Field of the Invention
The present invention relates to a method of reversible selective manifestation of different states of a functional element, which comprises at least two compounds and is capable of alternatively assuming two different states, by controlling the respective conditions for attaining the two states.
2. Discussion of the Background
The utilization as a reversible functional element of a material capable of assuming a plurality of stable different states and being transferred among those different states as desired by the application of some stimuli thereto is conventionally known.
As such reversible functional elements, for instance, functional elements are known which utilize the reversible thermal transformation of a crystalline state, a molecular arrangement, or an aggregation state, such as a display element which utilizes the reversible changes in the molecular arrangement of liquid crystalline compounds by the application of an electric field or heat, and an information recording element which utilizes a reversible transformation between an amorphous state and a crystalline state of an inorganic compound or an organic compound, a reversible transformation between two different crystalline states, or a reversible transformation between two different association states of molecules.
Although some of these conventional elements are already widely used in practice, they leave much room for improvement because of the complexity of the structure thereof, the complexity of systems using the elements, and the poor contrast of displayed or recorded images.
There are also known functional elements which utilize reversible changes in molecular structure, such as photochromism and electrochromism. Almost none of such elements is used in practice because they have problems related to repeated operation performance and response speed.
A reversible functional element which utilizes a reversible reaction between two compounds has also been proposed. An example of such a reversible functional element which has been put to practical use is a thermosensitive coloring element which utilizes a coloring reaction between an electron-donor coloring compound and an electron-acceptor compound. The function of this thermosensitive coloring element can be manifested by the application of heat thereto, so that it assumes a colored state. Further, depending on the materials employed in the coloring element, it is possible to reversibly change its state from the colored state to a decolorized state.
Reversible thermosensitive coloring elements of this type, however, have the following shortcomings: A long time is required to return to a decolorized state from a colored state. A decolorizing agent is necessary. An additional treatment using an organic solvent or water is also necessary. Furthermore, once the reversible thermosensitive coloring element has been colored, it reassumes the initial decolorized state only with great difficulty.
Accordingly, an object of the present invention is to provide a method of reversibly and selectively manifesting different states of a functional element easily and speedily, free from the above-mentioned conventional shortcomings.
The above-mentioned object of the present invention can be achieved by a method of reversible selective manifestation of different states of a functional element, which comprises at least two compounds and is capable of alternatively assuming (a) a first state in which the two compounds interact to form a regular aggregate structure, or (b) a second state in which the two compounds do not interact, and at least one of the two compounds is in an aggregate or crystallized state, by controlling the respective conditions for attaining one of the two states.